This invention relates to a method for tracking the location of mobile agents using the stand-off optical technique, light detection and ranging (LIDAR), which is also called laser radar (LADAR). There are a number of apparatus patents describing LIDAR optical systems. The method of multi-dimensional mapping of the location of mobile agents using a LIDAR system is a novel aspect of this invention.
Zaromb (U.S. Pat. No. 3,768,908) reports a LIDAR remote sensing apparatus comprising a laser transmitter and a receiver in which the radiation return is spectrally analyzed, a fluorescent target at a considerable distance from said transmitter and receiver, and means for aiming said transmitter and receiver at said fluorescent target. The presence of pollutants between the LIDAR system and said target is deduced from the attenuation of the radiation return at several wavelengths or from the Raman backscatter due to specific air pollutants.
Cecchi and Pantini (U.S. Pat. No. 5,096,293) report a multichannel fluorescence lidar comprising a source for the emission of a laser beam, an optical receiving system to focus the backscattered radiation, and an optical channels separator and means for processing the detected signals. The device comprises means for forming the ratio, two by two, of the signals originating from the optical channels separator and means for making the comparison between the values of the ratios and a series of values stored in an archive or a data base.
Moran et al. (U.S. Pat. No. 5,270,780) report a LIDAR system using dual detectors to provide three-dimensional imaging of underwater objects (or other objects hidden by a partially transmissive medium). One of the detectors is a low resolution, high bandwidth detector. The other is a high resolution, narrow bandwidth detector. An initial laser pulse is transmitted to known x-y coordinates of a target area. The photo signals returned from the target area from this initial pulse are directed to the low resolution, high bandwidth detector, where a preliminary determination as to the location (depth, or z coordinate) of an object in the target area is made based on the time-of-receipt of the return photo signal. A second laser pulse is then transmitted to the target area and the return photo signals from such second laser pulse are directed to the high resolution, narrow bandwidth detector. This high resolution detector is gated on at a time so that only photo signals returned from a narrow “slice” of the target area (corresponding to the previously detected depth of the object) are received. An image of the detected object is then reconstructed from the signals generated by the high resolution detector. In a preferred embodiment, the two detectors are housed in a single digicon tube, with magnetic deflection being used to steer the beam to the appropriate detector.
Fry (U.S. Pat. No. 6,388,246) reports a system for detecting an underwater object including an optical signal generator operable to generate and transmit an optical signal into the water. The system also includes an absorption cell operable to receive the optical signal reflected from the water and absorb an unshifted frequency component of the reflected optical signal. The system further includes a detector operable to receive a shifted frequency component of the optical signal from the absorption cell and detect the object using the shifted frequency component of the optical signal. Displacement of the water by the object causes an absence of a portion of the shifted frequency component of the optical signal.
Cooper and Vujkovic (U.S. Pat. No. 6,518,562) report a method and apparatus for the mobile and remote detection of a gas, such as methane, in the atmosphere. The apparatus includes a tunable-diode-laser (TDL)-based Light Detection and Ranging (LIDAR) driven at carrier frequency lying within the absorption line of the gas. The apparatus also drives the TDL with a modulation frequency to generate upper and lower sidebands in the output of the TDL and with a low ramp frequency to sweep the output of the TDL across twice the width of the pressure-broadened absorption line of the gas, preferably the first overtone absorption line in the case of methane detection. Suitable power for remote detection through use of the TDL is provided by a master oscillator/fiber amplifier transmitter has no moving or adjustable parts at all. An all-solid-state monolithic and integrated amplifier is achieved, which leads to a compact and virtually maintenance-free LIDAR system. The remote detection apparatus includes reference and calibration cells or chambers, and includes a light collector and detectors to detect the quantity and modulation of the light that passes the reference or calibration cells and that is received by the apparatus after reflection back toward the apparatus from an uncooperative target. The apparatus further includes a signal processor that applies a derivative spectroscopy technique, such as frequency modulation spectroscopy or wavelength modulation spectroscopy, to determine the presence of the gas in the atmosphere.
Ray and Sedlacek. (U.S. Pat. No. 6,608,677) report a method and apparatus for remote, stand-off, and high efficiency spectroscopic detection of biological and chemical substances. The apparatus including an optical beam transmitter which transmits a beam having an axis of transmission to a target, the beam comprising at least a laser emission. An optical detector having an optical detection path to the target is provided for gathering optical information. The optical detection path has an axis of optical detection. A beam alignment device fixes the transmitter proximal to the detector and directs the beam to the target along the optical detection path such that the axis of transmission is within the optical detection path. Optical information gathered by the optical detector is analyzed by an analyzer which is operatively connected to the detector.
An application of LIDAR technology to tracking the location of honey bees is described in “Tracking Honey Bees Using LIDAR (Light Detection and Ranging) Technology, S. Bender, P. Rodacy, R. L. Schmitt, P. J. Hargis, Jr., M. S. Johnson, J. R. Klarkowski, and G. I. Magee, SAND Report SAND 2003-0184, (Sandia National Laboratories, Albuquerque, N. Mex., 2003).